1. Field of the Invention
The present invention relates to a starting clutch which can be used in place of a torque converter of a motor vehicle.
2. Related Background Art
Conventionally, in an AT (automatic transmission), a vehicle was started by transmission of torque in a torque converter. Since the torque converter had a torque amplifying effect and torque could smoothly be transmitted during increase and decrease of the torque, the torque converter was mounted to many AT motor vehicles.
On the other hand, the torque converter has a disadvantage that a slip amount is great during increase and decrease of the torque and thus not so efficient.
Thus, recently, use of a starting clutch in place of the torque converter has been proposed, and torque has been amplified at a low speed area by decreasing a gear ratio and increasing a transmission number.
FIG. 2 is an-axial sectional view of a conventional starting clutch. Now, such a starting clutch will be explained. The starting clutch 100 includes a multi-plate clutch 101. Within a clutch case 106 of the multi-plate clutch 101, friction plates 102 acting as output side friction engaging elements and separator plates 103 acting as input side friction engaging elements are alternately disposed.
Further, a backing plate 104 is provided at one axial end of the multi-plate clutch. The backing plate 104 is supported by a stop ring 105 at an axial outer side (left in FIG. 2). On the other hand, at an end opposite to the backing plate 104, a piston 108 is disposed within an inner wall of the clutch case 106 through an O-ring 107. The piston 108 is biased by a return spring 116 toward a direction (right in FIG. 2) along which an engaging condition between the separator plates 103 and the friction plates 102 is released. Further, a hydraulic chamber 109 is defined between the piston 108 and the clutch case 106.
The starting clutch 100 further includes a housing 110 covering an outer periphery of the multi-plate clutch 101, and a damper 117 disposed between the clutch case 106 and the housing 110. Incidentally, the housing 110 is connected to an output shaft 111 of an engine (not shown) and the damper 117 is constituted by a spring 130, a retainer plate 113 for holding the spring 130 and a pawl 114 engaging by the spring 130.
In the above-mentioned starting clutch 100, the piston 108 is operated by supplying hydraulic pressure into the hydraulic chamber 109 through an oil path 115, thereby effecting frictional engagement between the separator plates 103 and the friction plates 102.
As mentioned above, in the starting clutch 100, the piston 108 is operated by supplying the hydraulic pressure into the hydraulic chamber 109 through the oil path 115, thereby effecting the frictional engagement. That is to say, upon operation of the starting clutch (upon transmission of power), the hydraulic pressure always acts. A predetermined clearance is provided, and, since the clearance is maintained by a biasing force of the return spring 116 against the piston, torque is completely blocked upon releasing.
When it is desired to release the engaging condition between the separator plates 103 and the friction plates 102, the hydraulic pressure is released. When the hydraulic pressure is released, the piston 108 can be moved freely and thus is shifted to the right in FIG. 2 by the biasing force of the return spring 116. As a result, the engaging condition between the separator plates 103 and the friction plates 102 is released.
However, in order to maintain the frictional engaging condition between the separator plates 103 and the friction plates 102, the hydraulic pressure must always be supplied. Further, an operating time of a pump for supplying the hydraulic pressure to maintain the hydraulic pressure becomes longer. And, a mechanism can be complicated.
Therefore, an object of the present invention is to provide a starting clutch in which hydraulic pressure is not required to always be supplied, and an operating time of a pump for supplying the hydraulic pressure can be shortened, and operating efficiency is enhanced.
To achieve the above object, the present invention provides a starting clutch in which an input side element and an output side element are joined together by applying an axial load thereby to transmit a power, which clutch comprises urging means for always providing the axial load, and releasing means for releasing the input side element and the output side element from the axial load.
Further the present invention provides a method for controlling a starting clutch, in which the clutch is released by supplying hydraulic pressure and the clutch is engaged by releasing the hydraulic pressure.
Since the input side element and the output side element are frictionally engaged together by the spring for always providing the axial load and a hydraulic cylinder for releasing the input side element and the output side element from the axial load is provided, in the operation of the starting clutch, the hydraulic pressure may be supplied only upon releasing the clutch, with the result that the operating time of the pump for supplying the hydraulic pressure is shortened thereby to enhance the operating efficiency. Further, since the urging load given by the spring is provided by the mechanical means, good stability can be achieved. Accordingly, stable control can easily be performed.
Since the clutch is released by supplying the hydraulic pressure and the clutch is engaged by releasing the hydraulic pressure, a starting clutch controlling method in which operating efficiency is enhanced can be provided.